The broad objective of this investigation is to increase our understanding of the pathogenic mechanisms of Pseudomonas aeruginosa in chronic respiratory inspections of cystic fibrosis (CF) patients. The ability of P. aeruginosa to maintain chronic respiratory infections in CF patients is associated with the organism's ability to convert to an alginate-secreting (Alg+) form. Alginate is a capsule-like exopolysaccharide, and its production gives P. aeruginosa a mucoid colony morphology. Using genetic and molecular approaches, this project proposes to elucidate various steps in the pathway of alginate biosynthesis; an alginate gene (algB) cloned from the P. aeruginosa chromosome will be characterized to determine the size and function of the polypeptide product, its cellular localization, regulation and genetic organization. Other genes whose products are directly involved in alginate biosynthesis will be cloned and characterized. Also, this study will determine the nature of the mechanism which activates genes for alginate biosynthesis in P. aeruginosa; these regulatory (algR) genes, recently clone will be physically analyzed to determine the mechanism of alginate conversion. The cis activation by algR of structural and/or regulatory genes involved in alginate production will be examined. In addition, this research endeavor will investigate the nature of the regulatory mechanism responsible for reduced extracellular enzymes in Alg+ strains; gene fusion technology will be employed to determine the effect of the Alg+ trait on protease transcription and secretion.